-LRB- CNN -RRB- One would expect that the U.S. Environmental Protection Agency has the best interests of the public in mind , but its recent decisions have cast serious doubt upon this assumption .

One in particular could have a dramatic impact on the safety of the U.S. food supply : It is the mandate of the EPA to regulate the use of agricultural chemicals like insecticides and herbicides , as well as to determine their allowable limits in food and drinking water .

Herbicides -LRB- weed killers -RRB- are mixtures of chemicals designed to spray on weeds , where they get inside the plants and inhibit enzymes required for the plant to live . The active ingredient in the most widely used herbicide is glyphosate , while some herbicides contain 2,4 D. 2,4 D is best known as a component of Agent Orange , a defoliant widely employed during the Vietnam War . Until the introduction of GM crops about 20 years ago , herbicides were sprayed on fields before planting , and then only sparingly used around crops . The food that we ate from the plants was free of these chemicals .

In stark contrast , with herbicide resistant GM plants , the herbicides and a mixture of other chemicals -LRB- surfactants -RRB- required to get the active ingredient into the plant are sprayed directly on the crops and are then taken up into the plant . The surrounding weeds are killed while the GM plant is engineered to resist the herbicide . Therefore , the food crop itself contains the herbicide as well as a mixture of surfactants .

To accommodate the fact that weeds are becoming glyphosate resistant , thereby requiring more herbicide use , the EPA has steadily increased its allowable concentration limit in food , and has essentially ignored our exposure to the other chemicals that are in its commercial formulation .

As a result , the amount of glyphosate-based herbicide introduced into our foods has increased enormously since the introduction of GM crops . Multiple studies have shown that glyphosate-based herbicides are toxic and likely public health hazards .

Of equal importance in terms of health is the fact that herbicides are now being used to rapidly kill non-GM grain crops at the end of their growing season in order to speed up harvesting . So , a product can be labeled GM-free but still contain high levels of herbicide .

The fact that agricultural chemicals are now inside the food crops that we eat is a fundamental shift in both our food production system and human exposure to toxic chemicals . Unfortunately , it is about to get even worse .

Since 2,4 D has been used for over 50 years , its toxicity to farm workers and neighboring populations is well documented . EPA sponsored studies have shown that those repeatedly exposed to 2,4 D have an increased risk of Parkinson 's disease , cancer and birth defects . Its nonagricultural use is banned in some European countries .

Despite this information , and warnings from many knowledgeable organizations , scientists and doctors , the EPA has recently concluded that the commercialization of corn and soy genetically modified to be resistant to both 2,4 D and glyphosate will have no adverse effects on human health and has allowed the introduction of these crops in many states . The summary statements used to justify this decision are on the EPA website , but the scientific data and discussion to support it are not available to the public .

Some predict that because of these GM crops and the inevitable increase in weed herbicide resistance , the amount of 2,4 D entering our environment could soon increase up to 30 fold over the 2010 levels .

As a medical research scientist , I consider this EPA allowance a grave error and believe that it will ultimately lead to a public health disaster . This conclusion is based upon the following considerations :

1 -RRB- 2,4 D , glyphosate , and surfactants are inside the plant and can not be washed off . Recently shipments of soybeans to Asia have contained 50-fold the amount of glyphosate allowed in Europe , and high levels are in U.S. GM soybeans while none is detected in conventional and organic beans .

2 -RRB- 2,4 D is toxic , and safety testing of glyphosate formulations has shown that they are endocrine disrupters and cause liver and kidney damage . Moreover , it appears that the specific formulation of 2,4 D and glyphosate that will be applied to the new GM crops has not been tested for health safety . Because soy - and corn-based foods will contain these chemicals , they should be considered food additives and fall under the jurisdiction of the FDA , which would require extensive safety testing . Currently none are required .

3 -RRB- Glyphosate and 2,4 D accumulate in the environment , and the amounts will increase in our food and drinking water as their combined use becomes widespread and weeds become more resistant . Glyphosate is already found in the blood and urine of people , and in a soy rich nutrient mix given to infants .

4 -RRB- While the producers of the new , doubly herbicide resistant crops and the U.S. regulatory agencies have some control over the production and use of herbicides in this country , they can not control those made or used abroad . The relatively uncontrolled use of glyphoshate-based herbicides in South and Central America has lead to significant increases in birth defects , kidney toxicity , and cancer . It will be much worse if 2,4 D is thrown into the mix .

What does this all mean ? Consumers should consider purchasing certified organic soy and corn products until the EPA withdraws its allowance of food crops that contain herbicides , and every effort should be made to prevent the introduction of additional herbicide resistant crops . These food additives are not good for you or your children .

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EPA has steadily increased the allowable concentration limit of herbicides in food supply

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David Schubert : Herbicide resistant crops present health risks for consumers that can not be ignored